Press with tie bar mechanism

ABSTRACT

A PRESS HAVING A PAIR OF PLATENS BETWEEN WHICH AN OBJECT TO BE PRESSED IS LOCATED. AT LEAST ONE OF THE PLATENS IS MOVABLE TOWARDS AND AWAY FROM THE OTHER TO ADJUST THE SPACING BETWEEN THE PLATENS. AFTER SUCH SPACING HAS BEEN ADJUSTED, A PAIR OF STURDY TIE BARS ARE MOVED TO ENGAGE   BOTH PLATENS AND LOCK THEM TOGETHER. FORCE IS THEN APPLIED TO THE OBJECT, THE RESULTANT REACTION FORCES BEING RESISTED BY THE LOCKED TOGETHER PLATENS.

LADISLAO (WLADYSLAW) PUTKOWSKI PRESSA WITHTIE BAR MECHANISM I YFiled Nov; 5.' 1969 6 sheets-sheet 1 PUTKOWSKI LADlsLAo (wLADYsLAw) Sept. 21, 1971 LADlsLAo (wLADYsLAw) PurKowsKl PRESS-WITH TIE BAR MECHANISM 6 Sheets-Sheet 2 Filed Nov. 5, 1969 lNvlfN'm/z.

PuTKowsKl n, ppm

LADISLAO (WLADYSLAW) sept. 21, 1911 3,606,636

LADISLAO (WLADYSLAW) PUTKOWSKI PRESS WITH TIE BAR MECHANISM Filed NOV. 5, 1969 6 Sheets-Sheet 5 INVENTOR. LADISLAO (WLADYSLAW) PUT KOWSKI BY ua, Baak, y Da/u,

sept. 21, 1911 3,606,638

LADISLAO (WLADYSLAW) PUTKOWSKI PRESS WITH TIE BARMECHANISM Filed Nov. 1S, 1969 6 Sheets-Sheet 4 lfvVl;` (Ikl LADISLAO (WLADYSLAW) PUTKOWSKI Sept. 21, 1971 3,606,638

LADISLAO (WLADYSLAW) PUTKOWSKI PRESS WITH TIE BAR MECHANISM Filed NOV. 3, 1969 6 Sheets-Sheet 5 /Nv/v'/ 0R. LADlsLAo (wLADYsLAw) PuTKowsKl LADISLAO (WLADYSLAW) PUTKOWSKI PRESS WITH TIE BAR MECHNISM Filed Nov. 5, 1969 6 Sheets-Sheet 6 BOO FIIG

lNVl'iN'lUR. LADI SLAO (WLADYSLAW) PUTKOWSKI 5MM, l

United States Patent() Continuation-impart of application Ser. No. 623,929, Mar. 17, 1967. This application Nov. 3, 1969, Ser.

Int. Cl. B29c 3/00 AnsTRACT oFY THE VDISCLOSURE Y A press vhavingV a pair of platens between which an object to be pressed is located. At least one of the platens is movable towards and away from the other to adjust the spacing between the platens. After such spacing has been f7 Y adjusted, a'pair of sturdy tie bars are mo'ved to engage both platens and 'lock them together. Force is then applied to the object, the resultant reaction forces being resisted by the locked together platens.

This application is a continuation-in-part of my application S.N. A623,929 iiled Mar. 17, 1967, now abandoned.

. .This invention relates to a press for applying forces to i' objects. More particularly, it relates to a press having a pair of platens, at least one of which is movable, and a tie bar mechanism to lock the platens together.

In the4 past, presses capable of applying orwithstanding high forces, and yet also capable of acting through long strokes, have required very heavy and expensive structural components. For example, hydraulic presses capable of acting through a long stroke require lengthy. and correspondingly heavy piston and cylinder structures. In the result, the cost of high power, long stroke presses has been undesirably4 high.

Accordingly, it isan object of the present invention to provide a simplied press which combines a long stroke with capability for high power. In a typical embodiment of the invention, this is achieved by providing a pair of platens, one stationary and the other movable. Appropriate force applying means, such as a hydraulic piston and lcylindercan be ttedto either or both of the platens.

FIG. 4 is a side sectional view of a portion of the movable platen and one tie bar of the apparatus of FIGS. 1 to 3, showing in more detail the manner in which the teeth ofthe tie bar and platen engage;

FIG. 5 is a side sectional view of a pair of platens for use in the apparatus of FIG. 1 and adapted for use in pressure molding;

FIG. 6 is a perspective View, partly exploded, of a portion of a second embodiment of the present invention;

FIG. 7 is a side sectional view illustrating a modification of the embodiment of FIG. 6;

FIG. 8 is a side sectional View showing a portion of a modification of the apparatus of FIG. l;

FIG. 9 is a side sectional View showing a portion of a third embodiment of the invention;

FIG. 10 is a side view showing engagement of camming surfaces on a tie bar and tie bar puller of the embodiment of FIG. 9;

FIG. 1l shows in perspective a portion of the tie bar puller of FIG. 9;

FIG. 12 shows in perspective a portion of the tie bar of FIG. 9;

FIGS. 13 and 14 are sectional and perspective views respectively of a further embodiment of the invention; and

FIG. 15 shows a modified tooth design for the tie bars and platens.

Referring rstly t0 FIGS. 1 to 3, there is shown a press generally indicated at 2 and including a pair of side guide structures 4 and 6. Between the side guide structures is located a lower stationary platen 8. The platen 8 is connected to the guide structures 4 and y6 by means of bolts 10 extending through the side faces of the platen 8 (FIGS. 1 and 2). Since the bolts 10 are not required to absorb any of the forces generated during a pressing operation, they may be of relatively light construction. If desired, locating pins and keys may be used instead of the bolts 10.

Also provided is an upper movable platen 12. Platen 12 is supported by a shaft 14 extending upwardly, through a top plate 16 connected between the two side guide structures, into a piston and cylinder arrangement diagrammatically indicated at 18. The piston and cylinder 18 serve to raise and lower the platen 12 along a path of travel The movable platen is moved to a desired distance from A* the stationary platen (the distance depending on the dimensions of the object to be pressed) and the platens are then locked together against movement apart relative to each other by a pair of sturdy tie bars. After the platens have beenV locked together, the hydraulic or other press means between the platens is actuated to exert pressure upon the object to be pressed. In the result, since the reaction forces created during the pressing operation are transmitted through the platens to the tie bars, rather than being imposed upon the mechanism lfor movingl the movable platen through its relatively long stroke, such mech-y anism for moving the movable platen may be of relatively light construction and power. e

Further'objects and advantages of the invention will appear from the following disclosure, taken together with the accompanying drawings, in which:

FIG. l is a side sectional View, partly .broken away, of a iirst embodiment of the present invention showing the tie bars engaging the movable platen; l

A FIG. 2 is a top sectional view taken along. liney 2-2 of FIG.l l, looking down on one tiebar and its actuating linkage; Y ,t

:.FIG. 3 is a side view of' a portion of the apparatus of FIG. 1, showing the tops of the tie bars asretracted away from the movable platen;

indicated by arrow A in FIG. l, the platen 12 being guided during its movement -by flanges 20 (FIG. 2) which fit into cooperating channels 22 in the platen 12 (see also the modilication of FIG. 6, where primed reference numerals indicate corresponding parts).

Since the piston and cylinder 18 are used only to raise and lower the Aplaten 12, and not to exert any of the forces required during a pressing operation, they may be of relatively light construction. Other types of actuators, such as toggles, gears, racks, etc., may also be used to raise and lower platen 12.

The platen 12 is formed with a cylinder 24 in its lower surface. Fitted in the cylinder 24 is a piston 26 actuated hydraulically by fluid supplied through an orifice 28 in the cylinder. The piston 26 serves to apply pressure, during a pressing operation, to an object 27 (shown in dotted lines) between piston 26 and the stationary lower platen 8. After the pressing operation, when the fluid pressure in the cylinder 24 is reduced, the `piston 26 is retracted by spring retractors 30.

During a pressing operation, the platens 8 and 12 are locked together by a pair of sturdy, elongated tie bars 32 and 34. The tie bars are connected lto the platens as follows. Near their lower ends, the tie bars are connected, by bolts 36, 38, to bushings 40, 42 respectively. The bushings are supported by pivot pins 44, 46 in a position to bear against rounded bearing surfaces or channels 48, 50 in the undersurface of stationary platen 8. It should be noted that pivot pins 44, 46 serve only to support the weight of the tie bars 32, 34 and are not required to absorb any of the forces generated during a pressing operation. Instead, such forces are conducted from the stationary platen 8 to the tie bars 32, 34 by pressure of the rounded bearing surfaces 48, 50 on the bushings 40, 42 and then are conducted through the tie bars to the upper platen 12 as will be described shortly.

The upper portions of the tie bars 32, 34 are provided, at their surfaces facing the movable platen 12, with downwardly slanting sets of teeth 52, 54 respectively. These sets of teeth mate with cooperating sets of teeth 56, 58 respectively on the side faces of platen 12 facing the tie bars 32, 34. It will be noted that the teeth are generally triangular in cross section, with a relatively long pitch and consequently with relatively thick roots, so as better to withstand forces tending to shear them off during a pressing operation.

In the view shown in FIG. 1, the teeth on the tie bars and on the platen 12 are engaged, so that the two platens are locked through the tie bars against movement apart relative to each other along the path of travel of platen 12, indicated by arrow A. Thus, during a pressing operation on an object between the platens, the forces tending to move the platens apart are transmitted from the lower platen 8 through the bushings 40, 42 to the tie bars 32, 40 respectively, and then through the cooperating teeth on the tie bars and the upper platen 12 back to the upper platen.

Means are provided to swing the tie bars away from the upper platen 12, so that the position of the upper platen can be adjusted as desired. These means comprise a pair of hydraulic actuating mechanisms 60, 61 pivotally connected at 62, 63 to the side guide structures, and connecetd through toggle linkages to the tie bars 32, 34. The toggle linkages are substantially identical for each tie bar, and only the linkage for tie bar 32 will be described, the linkage for tie bar 34 being denoted by corresponding reference numerals followed by an a.

The linkage for tie bar 32 consists of a piston rod 64 pivotally connected to a pair of links 66, 68. Link 68 is pivotally connected to another link 70 fixed to the top of tie bar 32, while link 66 is `-lixed to a bar 72 (best shown for bar 72a in FIG. 3) pivotally extending through the sides of the side guide structure 4. A further link 74 is fixed to the bar 72 at a position outside the guide structure 6, and is pivotally connected to a rod 75 extending across to corresponding link 74a of the toggle linkage for tie Ibar 34.

When it is desired to swing the tie bars 32, 34 away from the movable platen 12, in the direction of arrows B and C, in order that the position of platen 12 may be varied, the piston rods 64, `64a are moved upwardly.

Considering the operation Ifor tie bar 32, this upward movement of piston rod 64 pulls the connection of links 66, 68 upwardly (as shown in FIG. 3), and since link 66 is fixed to bar 72 (bar 72 being fixed against any movement other than rotation), link 70 and hence the upper end of tie bar 32 are moved in the direction of arrow B, thus disengaging the teeth 52 of the tie bar 32 from the teeth l56 of movable platen 12. Similarly, movement of piston rod 64a upwardly pivots the upper portion of tie bar 34 in the direction of arrow C, thus disengaging teeth 54 of tie bar 34 from the teeth 58 of the movable platen 12.

The connecting rod 75 is provided to assure that should one of the hydraulic mechanisms 60, 61 fail, the tie bars willstill pivot inwardly and outwardly in unison. For example, when piston rod l64 is pulled up to pivot the top of tie bar 32 outwardly in the direction of arrow B bar 72 rotates counterclockwise, thus causing rod 75 to move in the direction of arrow D, FIG. 3. This rotates link 74a: and bar 72a clockwise, thus forcing piston rod 64a upwardly and pivoting the top of tie bar 34 in the direction of arrow C.

Once the tie bars 32, 34 have been pivoted away from engagement with the movable platen 12, platen 12 may be moved upwardly or downwardly as desired by means of the piston and cylinder 18 acting through the rod 14.

In order to protect the tie bars and toggle linkages from dirt, blinds 76 are provided, connected between the lower side edges of the movable platen 12 and roll-up mechanisms 77 connected to the lower platen 8. Similar blinds 78 are connected between the upper side edges of the movable platen 12 and rollup mechanisms 79 located at the top of the side guide structures. The blinds run in grooves 80 in the side guide structures.

Thus, as the platen 12 moves upwardly, for example, the blinds 78 roll up and the blinds 76 unroll, thereby preventing dirt from entering the tie bar mechanisms. The blinds may alternatively be of metal slat construction.

In summary at this point, the steps that will typically be followed during a pressing operation with the apparratus of FIGS. 1 to 3 are as follows.

First, the tie bars 32, 34 are separated (if they were previously in engagement with the movable platen 12) by retracting the piston rods 64, 64a. Next, the movable platen 12 is moved upwardly until it is separated from the lower platens 8 by a distance suflicient that an object to be pressed may conveniently be inserted between the two platens.

After the object has been inserted, the movable platen 12 is moved downwardly by the piston and cylinder 18 to a position in which the piston 26 is adjacent the top of the object to be pressed,

It will be apparent that the platen 12 may be locked any one of a number of discrete position along its path of travel, the possible positions being spaced by a distance equal to the pitch of the teeth 52, 54, 56, 58.

After the platen 12 has been moved downwardly either to a desired position or until the piston 26 strikes the top of the object to be pressed, piston rods 64, 64a are forced downwardly to pivot the tie bars 32, 34 into a position in which their teeth engage the teeth on platen 12. The piston and cylinder 18 may be left actuated at this time if desired (so that they continue to force platen 12 downwardly), to eliminate the operation of turning piston and cylinder 18 off. The force exerted by piston and cylinder 18 is light and will be ineffectual once the teeth of the tie 'bars engage the teeth of the platen 12 or once the platen 12 strikes the top of the object to be pressed.

The manner in which the teeth of the tie bars engage the teeth of the movable platen 12 is shown in detail for tie bar 32 in FIG. 4. As shown in FIG. 4, a clearance, indicated by dimension x, is provided between the force transmitting surfaces 83 of the teeth 52 of tie bar 32 and the force transmitting surfaces 84 of teeth 56 of platen 12. The clearance permits the teeth of the tie bar to move without friction into engagement with the teeth of the platen as the tie bar 32 pivots from open to closed position. The clearance should be as small as possible consistent with permitting smooth engagement of the cooperating teeth. The teeth are chamfered as at 81,

82 to facilitate their smooth engagement.

In addition the force transmitting surfaces of the teeth 52, 56 have a slight negative slope, indicated by angle 9. In other words, surfaces 83 ofteeth 52 slope, from their root spaces to their tips, toward the stationary platen 8 by angle 0. Similarly, the force transmitting surfaces 84 of teeth 56 slope, from their root spaces to their tips, away from stationary platen 8 by angle 0.'

the stationary platen 8. The resultant reaction force drives the movable platen 12 upwardly to the position shown in dotted lines in FIG. 4, at which point the force transmitting surfaces of the teeth 52, 56 'engage and prevent further upward movement of platen'12. The force exerted on the tie bar teeth prevents the tie bars from pivoting out of engagement with the platen 12, as mentioned. l Y

'Possible pivoting of the tie bars out of engagement with the platen 12 is additionally resisted by the toggle linkages at the top of each tie bar. Specifically, links 66 Iand 68 form an over-the-centre toggle linkage abutting against the top of tie bar 32 and positively locking the top of tie'bar 32 against outward movementuntil piston rod 64 is'drawn upwardly. Forces tending to push tie bar 32 outwardly are transmitted to and resisted by the bar 72. The same over-the-centre toggle linkage is used for tie bar 34.

After the pressing operation is completed, hydraulic pressure in the cylinder 2-4 is reduced, and the piston 26 is then retracted by the spring retractors 30. The downward pressure exerted by piston and cylinder 18 on platen 12 then moves platen 12 downwardly to the solid line position shown in FIG. 4, unlocking the teeth of the platen from the teeth of the tie bars. The tie bar actuating mechanisms 60, 61 are then actuated to draw the piston rods 64, 64a upwardly, to disengage the tie bar.`- from the movable platen 12, and the movable platen may then be retracted upwardly by means of the piston and cylinder 18.

It will be apparent that, in the apparatus of FIGS. 1 to 3, the maximum stroke is not limited by the extent to which the piston 26 can be moved in its cylinder 24. Instead, the extent by which the piston 26 may be separated from the lower platen 8 (these being the surfaces that apply pressure to an object in the embodiment being discussed) is limited only by the distance through which the movable platen 12 may be moved. In addition, the length of the stroke over which pressure may be applied depends primarily on the length over which the platen 12V may be locked to the tie bars, i.e. it depends primarily on the length of the tie bars and the number of teeth provided thereon.

If desired, the stroke of the piston 26 may be limited to a distance slightly greater than the pitch of the teeth 52, 54, 56, 58 (i.e. the distance in the direction of arrow A between adjacent teeth). Then, after each stroke of the piston 26, the movable platen may be moved downwardly by a distance equal to the pitch of the teeth, a further stroke of the piston 26 then being taken. By this multiple stroke method, a long stroke may be executed at full power.

If desired, the platens may be adapted for use in pressure molding, as shown in FIG. 5. In FIG. 5 the stationary platen, indicated at 85, includes a cavity `86 adapted to receive a molding die and the object to be molded (not shown), while the movable platen, indicated at 87, contains a conventional exible diaphragm 88 clamped by a tube 89 communicating with a hose 90 through which pressure `iluid is admitted. A conventional elastic wear diaphragm 92 is provided to protect the diaphragm 88 against wear. The operation of the apparatus of FIGS. 1 to 3 employing platens las shown in FIG. 5 is similar to that already described for the apparatus o f FIG. 1, in that the platens are separated, the object to be molded (not shown) is placed together with a mold (not shown) in the cavity 86, the platens 85` and 87 are then brought together, andpressure is applied through the hose 90 to expand the diaphragms 88 and 92 to initiate molding. i

Reference is next made to FIG. 6, which illustrates a modification of the apparatus of FIGS. A1 to 3, primed reference numerals indicating corresponding parts. It should be noted that in FIG. 6, platens 8 and 12 are shown simply as at heavy plates, between which any desired pressing apparatus may be inserted. For example a hydraulic piston and cylinder may be placed on platen f8', the piston pressing upwardly against an object located between such piston and the platen 12.

i In the apparatus of FIG. 6, the tie bars (only one tie bar 32 is shown) are'moved bodily linearly inwardly and outwardly in the direction of arrows'fE, towards and'away from the platens 8 and 12', -instead of being pivoted. The means for moving the tie bars inwardly and outwardly are the same for each tie bar, and only that for tie bar 31 will be described;

To move the tie bar 32 into or out of engagement with the platens as just discussed, a tie bar pulling rod or puller 94 is provided, movable upwardly and downwardly in the direction of arrow F through a channel 95 in the rear surfaceof tie bar 32', i.e. in the surface of tie bar 32' opposite to the surface containing the teeth 52. Guide blocks 96 and 98 iixed to the'side guide structure 4 serve to guide the puller 94 in its up land down movement and also substantially to prevent up and down movement of the tie bar 32. (A slight clearance is provided, equal to the chamfer of the tie bar and platen teeth.) Movement of the tie bar 3.2' is thus substantially limited to movement in the direction -of arrows E, towards and away from the platens, as will be described shortly.

A link 100 is fixed to the upper end of the tie bar 32', and a pair of further links 102 are pivotally connected between link 100 and the puller 94. Similarly, a link 104 is xed to the lower end of the tie bar 32', with a further pair of links 106 pivotally connected between link 104 and puller 94. As shown in FIG. 6, and also in the modication of FIG. 7, when the tie bar 32 is disengaged from the platens 8 and 12', the links 102 t into the upper end of channel 9S, which end is enlarged for this purpose.

The tie bar 32 includes, in addition to the set of teeth 52 at its upper end, a further set of teeth 108 at its lower end, the teeth 108 facing in a direction opposite to the teeth 52'. The teeth 108 mate with a set of cooperating teeth 110 on the lower platen 8'. The lower platen 8 may if desired be made movable in the same manner as the upper platen 12', or it may (as will be assumed to be the case) be lixed to the side guide 4 (and to the other side guide, not shown) by bolts 112 (or locating pins and keys).

In operation of the FIG. 6 apparatus, the tie bar 32 is maintained in the position shown in FIG. 6 (in which it is disengaged from the platen 12') and the platen 12 is moved to a desired position by means of piston and cylinder 18'.

After the relative spacing between the platens has been adjusted as desired, the puller 94 is pulled upwardly in the direction of arrow F. This moves the ends of links 102, 106 connected to puller 94 upwardly, and since the tie bar 32 is blocked from upward movement by blocks 96, 98, it is forced toward the platens 8', 12', .to a position in which teeth 52' engage teeth 56 a'nd teeth 108 engage teeth 110. Thedimensions of the mechanism are made such that when the teeth on the tie bar 32 engage the teeth on the platens as mentioned, links 102, 106 are y aligned in a direction substantially parallel to arrows E.

i.e. substantially at right angles to the path of travel ofV rod 94. In practice, links 102, 106 will move very slight past the direction indicated by arrows E, and further movement of these links is then prevented by contact of links 106 with the lower end of the tie bar 32'. This provides in eifect an over-the-centre toggle arrangement which locks the tie bars in engagement with the platens.

The slope of the teeth 52', 56', 108, 110 may be either negative, zero (in which case the force transmitting surfaces of the teeth are placed in planes at right angles to the direction of travel of the platen 12), or slightly positive. However, if the slope is positive, such slope will normally be made slight, so that no significant forces are developed during a pressing operation. Typically the slope of the teeth will be slightly negative, as shown in FIG. 6, so that the tie bars will be pulled inwardly toward the platens during a pressing operation.

After theperssing operation is completed, the puller 94 is moved downwardly to disengage the teeth of the tie bar from those of the platens. A similar operation is performed for the other tie bar, not shown, thus freeing the platen 12 for movement away from the object to be pressed. Y

If desired, the apparatus of FIG.l 6 may be modified slightly as shown in FIG. 7 to provide for automatic movement of the tie bars 32', 34' into and out of engagement with the platens 8' and 12. The means for accomplishing this operation comprise a plate 114 connected to the movable platen 12 through springs 116 of stiffness greater than the force encountered in adjusting the position of the movable -platen 12. A pair of rods 118, 120 extend upwardly through the top cover 16' of the apparatus and carry a pair of cam plates 122, 124 respectively. The

cam plates 122, 124 include camming surfaces 126, 128

which engage a pair of camming bars 130, 132 pivoted at pins 134, 136 respectively fixed to the side guide assemblies 4', 6' respectively. The camming bar 130 is pivotally connected at 138 to the top of the puller 94 for tie bar 32', while camming bar 132 is connected at 140 to the top of a similar puller 142 for tie bar 34.

In operation, the movable platen 12' is moved downwardly by piston and cylinder 18 as before, and after it has moveddownwardly to a predetermined extent, platen 12' strikes the top of the object (not shown) located between the platens. Usually this object will be a mold (such as that shown in FIG. the height of which is accurately known.

At this point the downward movement of platen 12 is arrested. However, piston and cylinder 18 remains actuated and further downward movement of plate 114 is permitted by virtue of springs 116.

The cam plates 122, 124 are positioned so that as platen 12 strikes the top of the object between the platens, camming surfaces 126, 128 engage the camming bars 130, 132. Camming bars 130, 132 then pivot clockwise and counterclockwise respectively as plate 114 continues to move downwardly. This pulls the pullers 94, 142 upwardly to move the tie bars 32', 34' into engagement with the platens. The extent to which springs 116 may be compressed is suflicient to allow the teeth of the tie bars fully to engage the teeth of the platens, to lock the platens tirmly together through the tie bars.

After the platens have been locked together, a pressing operation may be initiated. During the pressing operation i piston an cylinder 18 remains actuated, to maintain springs 116 compressed.

When the pressing operation is completed and the high pressure means (not shown) for applying pressure to the object to be pressed are restored to their original state, f

from the platens. Upward movement of platen 12 maythen be initiated.

` The position of the movable platen 12 at which the tie bar s 32', 34' are to move inwardly into engagement with the platens may be controlled by adjusting the position of the cam plates 122, 124 on the rods 118, 120. In the ernbodiment shown, the adjustment is in discrete steps, the cam plates being fastened to the rods 118, 120 by means of bolts (not numbered)` but clamps may be used insteadl to hold the cam plates to the rods 118, 120. Notches 121 are provided in the rods 118, 120 to conform to the shape 8 of the camming surfaces 126, 128 when'the cam plates are adjusted upwardly or downwardly on the rods 118, 120.

It will be apparent that although it has been assumed in the foregoing description that the apparatus described is to be used to apply pressure to an object, the apparatus may readily be adapted to apply tensile forces to an ob-v ject (to stretch the object). The tensile forces may be applied in various ways, e.g. by devices fixed to the platens and capable of pulling with respect to each other in a direction along the path of travel indicated by arrow A or A'. In such event, the slope of the teeth in the embodiments shown will be reversed, as typically indicated in FIG. 8 where the double primed reference numerals indicate parts corresponding to those of FIGS. 1 to 3. It will be noted that the bushings 40", 42 are now on downwardly facing surfaces of the tie bars 32, 34" and the curved bearing surfaces 48, 50" are on upwardly facing surfaces of the lower platen 8", so that the platens 8", 12 can be locked through the tie bars against forces tending to push them together along the path of travelindicated by arrow A. Tie bars with two sets of teeth, similar to the FIGS. 6 and 7 embodiment, may also be used. Reference is next made to FIGS. 9 to 12, where another modification of the invention is illustrated. In the moditication now to be described, no auxiliary force applying means are required; instead, the nal closing pressure (or tension) on the object to be operated on is applied by camming action of the tie bar teeth against the teeth of the platens.

In FIGS. 9 to 12 only one tie bar, indicated at 150, is shown, associated with a movable platen 152 and stationary platen 154. The other tie bar will be the same as tie bar 150.

Tie bar 15()` includes teeth 156 cooperating with teeth `158 on the movable platen 152, and teeth 160 cooperating with teeth 162 on the stationary platen 154. The rear surface of the tie bar includes a camming portion 164 having a pair of camming surfaces 166, 168 both inclined to the direction of the path of travel (indicated by arrow A) of movable platen 152. Camming surface 166 is, as shown, inclined more steeply with respect to the path of travel than is camming surface 168.

A tie bar pulling rod 170 is provided similar to puller 94 of FIGS. 6 and 7. Pulling rod 170` includes a camming portion 172 having a pair of camming surfaces 174, 176 cooperating with camming surfaces 166, 168 of the tie bar 150. Camming surfaces 174, 176 are both 'inclined as shown to the-path of travel of platen 152, surface 174 being more steeply inclined than surface 176.

The Vtie bar pulling rod 170 slides against wear plates 178, 180 tixed to the side guide structure 182, and is moved in a direction parallel to the path of travel of platen 152 by means of link 183. Link 183 is pivotally connected to the end of pulling rod 170 and is powered by any conventional means, such as a hydraulic actuator (not shown). If desired, a toggle linkage arrangement similar to the toggle linkage shown in FIG. 1 may be used to pull (and push) and lock the puller rod 170.

As is apparent from FIGS. 9 and 10, when the puller rod 170 is moved downwardly so that its camming surface 174 engages camming surface 166 of the tie bar 150, the tie bar will be forced relatively rapidly in the direction of arrow G towards the platens. The tie bar is guided in its movement by pins 184 set slantingly into the side guide structure 182 and slidable in holes 185 in the tie bar 150. The reason for the slantwise motion of the tie bar will be explained shortly. f

As the puller 17()` continues to move downwardly, its camming surface 176 engages camming surface .168. The tie bar 150` is then moved more slowly (but with a greater mechanical advantage) in the direction of arrow G towards the platens as the puller i170 continues its downward movement. It is during this slower movement of the tie bar 150 towards the platens that pressure is appliedV by the platens to the object to be pressed. Such pressure is 9 caused by downward movement of upper platen '152, resulting from engagement of teeth 156, 158, as will now be described.

Teeth 158 of upper platen 152 have root spaces 186, tips A188, and force transmitting surfaces 190 sloping, from the root spaces to the tips, towards the lower fixed platen 154. Teeth 156 of the tie bar have root spaces 194, tips 196, and force transmitting surfaces 198 sloping, from the root spaces to the tips, away from the lower platen 154.

For a pressing operation to be carried out, movable platen 1'52 is moved to a position such as that shown in FIG. 9, in which the force transmitting surfaces 190 of teeth 158 will lie partly along the force transmitting surfaces 198 of teeth 156 when teeth 156 are moved into initial contact with teeth 158. Then as tie bar 150 continues to move in the direction of arrow G, surfaces 198 slide over surfaces 190 to cam and pull the movable platen 152 downwardly by a distance indicated by dimension y plus z in FIG. 9. This last downward movement of platen 152 provides the compressive force to be applied to an object between the platens.

It is apparentthat the dimensions of the object on which pressure is to be exerted must be such that the object contacts both platens when the upper platen is in a position such as that shown in FIG: 9, so that movement of platen 152 effected by tie bar 150' will then serve to exert force on the object. Alternatively, height adjusting plates may be used if desired.

As the tie bar 150 pulls the platen 152 downwardly, the resulting reaction forces tend to force the tie bar upwardly. These forces are resisted primarily by the engagement of the lower teeth 1160 of the tie bar with the teeth 162 of lower platen 154. For this purpose, teeth 160 of the tie bar and teeth 162 of the lower platen have force transmitting surfaces 200, 202 respectively sloping in the same direction as arrow G. Teeth 160, 162 are positioned so that their force transmitting surfaces engage and slide over one another as the tie bar moves towards the platens, so that in effect, the tie bar 150 is braced on and pulls against the lower platen 154. Any outward force components are resisted by the wear plates 178, 180 and the side guide structures (which are firmly fastened together).

The sope of force transmitting surfaces 190, 1198 'of the upper teeth, with respect to the path of travel A, will normally be equal in magnitude (though opposite in direction) to the slope of force transmitting surfaces 200, 202 of the lower teeth. This balances the apparatus during a pressing operation. However, such balancing, although desirable, is not essential, particularly at lower pressures, and thus the slopes of the upper and lower force transmitting surfaces may differ.

In summary `at this point, as puller 170 moves down, cam surface 174 moves over cam surface 166 to move the tie bar 150 towards the platens. The teeth of the tie bar do not engage the platen teeth during this part of the procedure. Next, cam surface 176 engages cam surface 168 and the tie bar moves more slowly towards the platens. The tie bar teeth now begin to engage the platen teeth, and begin to force platen 152 towards platen :154. Because of the high forces exerted on camming surface 176, surface y1'7'6 may if desired be constituted by a wear plate 203 l(FIG. l2).

In practice, the puller 170 will normally have at least two camming portions such as camming portion 172, and tie bar 150l wil have at least two camming portions such as camming portion 164.

In order to disengage the tie bar 150 from the platens after a pressing operation has been completed, camming portion 172 of the puller 170 includes a T-shapgd retracter 204 (FIG. l1) that slides in -a T-shaped slot 206 (FIG. l2) inthe camming portion 164i of the tie bar. The retracter 204 has sloped cam surfaces 208, 210` having the same slope as cam surface 174, and cam surfaces 212, 214 having the same slope as cam surface 176. Cam

surfaces 208, 210I cooperate with correspondingly sloped surfaces 216 in slot 206, while cam surfaces 212, 2.14 cooperate with corresponding surfaces 218 in slot 206. After a pressing operation, when puller 170 is pulled upwardly in the view of FIG. 9, earn surface 212 of the retracter 204 bears against corresponding cam surface 218 of the tie bar slot 206 and begins to retract the tie bar from the platens, and then, cam surfaceY 210 of the retracter bears against corresponding cam surface 216 of the slot to complete the retraction of the tie bar 150'.

Various modifications may be made in the mechanism just described. For example, camming surfaces 174, 176 may be formed by a single smoothly curved surface, instead of an angular surface as shown. Camming surfaces 166, 168 may be similarly curved. Alternatively, instead of the cam or Wedge type mechanism just described, a link mechanism may be used to force the tie bars towards the platens.

The teeth 156, 158, 160, 162 of the FIGS. 9 to l2 embodiment will normally be of antiriction material and will be greased to facilitate their engagement. They may alternatively be provided with roller bearings on their force transmitting surfaces. Teeth 158 may consist of one tooth, although commonly more would be used. The length of the high pressure stroke will be determined by the length of the force transmitting surfaces 190, 198, their slope, the slope of arrow G, and the position of upper platen 152 at the time when the tie bars are closed.

If desired, the apparatus of FIG. 1 may be arranged so that final pressure is applied by closing of the tie bars (as in the apparatus of FIGS. 9 to l2) simply by changing the slope of the teeth 40, 44 from a negative to a positive angle. It will also be apparent that tension, instead of pressure may be applied by the apparatus of FIGS. 9 to l2 by reversal of the slope of the teeth and of pins 184.

It should be noted with regard to apparatus such as that of FIG. 6 that, during a pressing operation, the tie bars may be stretched slightly by the reaction forces produced. Thus, if guide blocks such as blocks 96, 98 of FIG. 6 are used at each end of the tie bar, the guide blocks will have to be securely fastened to the side guide structure (indicated at 4 in FIG. 6). The problem may be avoided by providing guide pins and holes, such as pins 184 and holes 185 of FIG. 9, at one longitudinal location only along the tie bar. With such an arrangement, slight stretching and contraction of the tie bars will exert no forces on the side guide structure.

It has been assumed throughout the description that only two tie bars and two side guide structures are to be used. However, additional pairs of tie bars and side gulde structures may be employed, typically when the platens assume an elongated rectangular form.

If desired, the apparatus shown can be modified so that the tie bars are hingedly connected to the movable platen and pivot to engage teeth on the side surfaces of the other platen (which can be fixed or movable). For example, in FIG. 8 the platen, 8" can be a movable platen, moved by long stroke low power means such as the prston and cylinder 18 and rod or shaft 14 shown in connection with the FIG. 1 embodiment. Platen 12 of FIG. 8 can be fixed, or it can also be movable. Appropriate actuating means i(not shown) will move the tie bars towards and away from the teeth which they are to engage.

Reference is next made to FIGS. 13 and 14 which show specifically a press 300 having tie bars 302 mounted on a movable platen 304. The tie bars 302 extend into a recess 303 of the movable platen 304 and are hingedly connected thereto by hinge pins 305 which pass through the movable platen 304. In FIG. 13 only one side of the press and one tie bar are shown, but the other side of the press is identical to that shown. The movable platen 304 is moved upwardly and downwardly by a rod 306 connected to a long stroke low power piston and cylinder -.-315permitting-upand down movement of thenmovable actuator 308.

The movable platen 304 is guided during its up and down movement by fixedtie rods 310 .which can be either round or flat as desired (they are shown as round). Either two or four fixed'tie rods.310 can be used;-in the embodiment illustrated there are` four fixedy tie rods v3.10

which pass through holes 312 at each corner-of the-movable platen 304. The holes `312 are shaped to accommodate the fixed tie rods' 310 snuglybut slidably.

In addition to the movable `platen there is provided a fixed platen 314. The fixed'platen` 314 comprises yan upper locking plate 315 which co-operates with the'tie bars`302 in a manner to be described, and a lower pressure plate 316 (located below they movable. platen 304'). The upper and-lower plates315, 316fare tiedtogether by the fixed tie rods 310.

The locking plate 315 comprises a rectangular upper plate 315a, and a pair of `thickened edge'members 315b,

one ateachside of therupper/plate315rThe edge members 315b could be integral'with the upperpla'te 315481,but in the embodiment shown they aref fabricated as 'separate members and are held to the upper plate 315a by thev fixed tie rods 310. Specially, the fixed tie rods 310 each include at each end a shoulder 318, and a threaded smaller diameter shaft 318a projecting axially from the shoulder. The edge members 31511 rest against the shoulders 318 with the shafts 31811 projecting therethrough. The upper plate 315e rests on the edge members 315b with the shafts 318:1 projecting through holes in its corners, and nuts 319 are threaded onto the ends of the shafts 318a to hold the assembly together.

Similarly, the lower pressure plate 316 rests against the i.

of openings 320, one for each tie bar 302. Each opening 320 a first side face 321, formed on the upper plate 315a, and a second opposite side face 322 (FIG. 14), formed on the inner side surface of edge member 315b. The second side face 322 contains teeth 324 which face and are engagable with teeth 326 extending along the hinged tie bars 302. Each opening 320 isiof-suflicient size to allow the tie bar 302 passingthrough ittol be swung into and out of engagement with the teeth 324.v

The tie bars 302 are actuated by a pair of double acting hydraulic or air actuators 328 hingedly vconnected in recesses in the tie bars by hinge pins 330.` Each actuator 328 is connected between the tie bars 302 and'moves up and down with` the tie bars 302. Flexible hoses, not shown,

the actuators '328.

`are provided to .conduct hydraulic liuid or air to and from The actuators 328 can be of lightconstruction, because they need not hold the tie bars 302 so that their teeth engage with those of lthe fixed platen 314. Instead, lbcking pins 336 are provided, of generally roundcrosssection but having a flat `side indicated at 338. vThe locking pins 336 extend transversely through the upper plate 315a and pass through the openings 320 adjacent the sides 321 thereof. The dimensions of the locking pins 336, the ltie bars 302, the openings320 and the teeth 326, "324 are made such that when locking pins 336 are positioned as shown, with their-full" diameter between the tie bars 302 andthe' yfaces 321', the tiebar teeth-326 are held in tight engagement with the fixed platen teeth 324. Conversely',when the locking pins 336 are rotated so that theirflat surfaces 338 are parallel with the sides of the tiebars 302, then when the actuators 328 are retracted, the tie bars 302 will move so that their teeth disengage from those of the locking plate andthe-locking-.pins 336 can be used to cam platen 304. The locking pins 336 can be rotated between their locking and unlocking positions by any desired means, such as a control lever (not shown) fastened to their ends. ,-3,1

When the actuators328 are, operated. tofretract the tie bars 302;'-one side of the actuators 328 maymove and not the other, retracting only one tie" bar `302.y This will continue until the tie bar 302 that is betig'rnoved contacts its associated locking pin 336. At that point, furtherfetractin'of such tie bar is prevented, and the actuators 328, which continue to retract,l then will retract the other tie bar 302.ayvay from1the, engagementJwith thev teeth 324. This arrangement," by which the tie bar ractuators 328 exy"tend betweenrv the tiebars and pull one tie vb'ar against fthe other, vresults in a'simple and relatively inexpensive structure. If desired, actuators 328 fc'an'V besimple'springs whichf continuously pull I'the tie bars "toward each other, the tie -bars into engagement withteeth 324. "l

I Fixed to th'eunde'rside of the yr'nov'a'bleplaten 304 and 'fforming'a'part thereof isra short stroke high 'power-'actua'tor 342, typically a hydraulic piston and cylinderA further pressure plate 344 is fixed to the moving p'orti'on'of the actuator 342 Iand is moved thereby through a very short stroke. The platen 344 is guided during its movement by the fixed tie bars 310, which pass through holes 346 in the sides of the pressure plate 344.

.f .In-the embodiment shownin FIGS. 13 and; 14, the 30.

teethv.326, 3240f the tie. bars 302 and Iplaten-314 are sloped to resist movement'of the movable 4platen 302 upwardly towards -the locking plate 315, i.e. away from the lower pressure plate 316. The apparatus of FIGS. V13, .14 is thus suitablefor applying pressure to an'object. If the teeth 326, 324 were oppositely sloped, then they would resist'movement of plateni3`04 and locking plate'315 away from each other and thus would resist movement of platen -304 and pressurev plate 316 together, and then Vthe yapparatus of FIGS. 13, 14 would' be suitable for applying tension to an object. i y

Although the tie bar teeth 326 are shownl'as facing out- ;wardly', away from each other, they could vif desired ,face

` corner of the platens, then the reaction forces tending to pushhthe platens apart will not act uniformlyon.. the

platens. Instead therel will be twisting forcestending to force the platenslslightly out of parallelism.

Normally, this is not serious, but if very close parallelism of. the platens is needed, then a tooth design similar to that shown in FIG. l5 may be used, In FIG. l5, a tie bar is indicated at 400, and its teeth at 402. The teeth on the cooperating platen (n ot shown) willl correspond in shape'to teeth`402fl` he teeth 402 have front vforce transn'iitting surfaces 404 (whichy trans/mit most of the reaction :forces when thelobject under treatment is centred), and back surfaces 406. Inpthe FIG. 15 embodiment the.v angle x between the frontsurfacesj404 of the teeth andthe plane lperpendicular to the axis of the tie bar is equal to the angle y between the backsurfaces 406 o'fithe teeth and the plane perpendicular t0. the axis of the ,tiefban Because the yangles x andy. are equal, awedgingaction vis obtained which helps to, preventmovement ofthe tie bar-.and platen teeth relativetoeach other during ofcentre loading. The angles): and .y should beat least- 3 degrees to-.facilitate .disengagement ofthe teethand can be as great as about 15 degrees while still producing suitable wedging action.

A preferred value for angles x and y is about 7 degrees.

In order rto improve the strengthof teeth 402, these teeth are made relatively thick, as shown.

=What I claim as my invention is:

1. In a machine for generating forces along a pre determined path for application to an object, Vthe improvement comprising:

(a) first and second platens, each extending in a plane perpendicular to said path and each including first and second opposite sidevfaces,

(b) means supporting said platens in opposed relation,

(c) said platens including opposed force receiving means for receiving reaction forces produced as a result of application of generated forces to said object, said reaction .forces tending to move said platens in a predetermined direction relative toeach other along said path,

(d) said means supporting said platens in opposed relation including motive means for moving said first platen along said path towards and away from said force receiving means of said second platen,

(e) a pair of opposed elongated tie bars spaced parallel to each other and to said path and facing said side faces,

(f) said tie bars and said platens containing cooperating locking means engageable for locking said platens together through said tie bars against movement of said platens in said predetermined direction relative to each other along said path, said cooperating locking means including a plurality of teeth on said side faces of one of said platens, and a plurality of cooperating teeth extending along the surfaces of said tie bars facing said faces of said one platen,

(g) and means for moving said tie bars between a first fixed position in which said locking means are engaged, and a second position in which the locking means of said tie bars are disengaged from at least the locking means of said one platen, said tie bars being substantially parallel to each other and to the direction of said path when in a said first position.

2. Apparatus according to claim 1 wherein said one platen is said first platen.

13. Apparatus according to claim 1 wherein said cooperating locking means includes hinge meansv connecting said tie bars to the other of said platens, and said means (g) includes means for pivoting said tie bars about said hinge means.

4. Apparatus according to claim 2 wherein said cooperating locking means include a further plurality of teeth on said 'opposite side faces of said'second platen, and further cooperating teeth extending along the surfaces of said tie bars facing said side faces of said` second platen, and said means (g) includesrmeans for moving said tie bars in a substantially linear path towards and away from said platens.

5. Apparatus according to claim 4 wherein said substantially linear path of movement of said tie bars towards and away from said platens includes a component of movement parallel to said path of travel, so that said cooperating teeth of said tie bars may engage the teeth of said one platen to pull said one platen along said path of travel as said tie bars are moved to their first position.

6; In a press for applying pressure to an object in a direction along a path of travel, the improvement comprising:

(a) first and second platens, said platens extending in a plane perpendicular to said path of travel and each including a pair of opposite side faces,

(b) means supporting said platens in opposed relationship and including means for moving said first platen towards and away from said second platen along said path of travel,

(c) said platens including opposed force receiving means for receiving reaction forces produced as a result of application of pressure to said object, said f4 reaction forces tending to move said platens apart relative to each other along said path of travel,

(d) a pair of elongated tie bars spaced on opposite sides of said platens facing said side faces,

(e) the side faces of said first platen each including first locking means,

(f) said second platen including second locking means,

(g) said tie bars each including third locking means extending therealong and engageable with said first locking means when said first platen is in any of a plurality of positions along said path of travel, and fourth locking means engageable with said second locking means; said third and fourth locking means, when engaged with said first and second locking means respectively, locking said platens together through said tie bars against movement of said platens apart along said path of travel,

(h) and means for moving said tie bars between a first xed position in which said third and fourth locking means engage said first `and second locking means respectively, and a second position in which at least said third locking means are disengaged from said first locking means,

whereby, during a pressing operation, said tie bars are moved to their second position by said means (h), said first platen is moved away from said second platen by said means (b), said object is inserted between said platens, said first platen is moved toward said second platen by said means (b) until it is in a desired one of said plurality of positions, and said tie bars are moved to their first position by said means (h) thus to lock said platens, through said tie bars, against movement apart along said path of travel.

7. Apparatus according to claim 6 wherein said platens include cooperating mold cavities, one of' said cavities being adapted to receive a flexible diaphragm, and the other being adapted to receive a mold, for use in pressure forming.

8. Apparatus according to claim 6 wherein said first locking means comprise teeth on said side faces of said first platen and spaced apart in a direction parallel to said path of travel and said third locking means comprise cooperating teeth on the surface of said tie bars facing said platens.

9. Apparatus according to claim 8 wherein said second and fourth locking means together comprise hinge means connecting said tie bars to said second platen, and said means (h) comprises means for pivoting said tie bars about said hinge means, said first position of said tie bars being a position in which said tie bars both extend parallel to said path of travel, and said second position of said tie bars being a position in which said tie bars are pivoted apart from each other about said hinge means.

10. Apparatus according to claim 9 wherein said teeth of said first platen have tips and root spaces and force transmitting surfaces sloping, from said root spaces to said tips, away from said second platen; the teeth of said tie bars having tips and root spaces and force transmitting surfaces sloping, from such root spaces to such tips, towards said second platen, so that during a pressing operation with said platens locked together through said tie bars, the reaction forces produced and tending to force said platens apart will tend to pull said tie bars more firmly into engagement with said first platen.

11. Apparatus according to claim 9 wherein said tie bar has an end remote from said hinge means; and wherein said means (h) includes: a pair of tie bar actuating means, one for each tie bar, and toggle linkage means connecting each of said tie bar actuating means to said end of its associated tie bar, said toggle linkage means including means for positively locking said tie bars, when said tie bars are in said first position, againt movement apart l toward their second position in the absence of further actuation of said tie bar actuating means.

12. Apparatus according to claim 11 including connecting rod means extending between said toggle linkage means of each tie bar, and means connecting said connecting rod means to each said toggle linkage means for movement of one tie bar from one of its first and second positions to the other of its first and second positions to effect, through said connecting rod means, corresponding movement of the other tie bar from a corresponding one of its positions to a corresponding other of its positions.

13. Apparatus according to claim 8 wherein said second locking means comprise further teeth on said side faces of said second platen, said further teeth being spaced apart in a direction parallel to said path of travel, and said fourth locking means comprise further cooperating teeth on said tie bars, said second position of said tie bars being a position in which said second locking means are disengaged from said fourth locking means.

14. Apparatus according to claim 13 wherein the teeth of each of said platens have tips and root spaces, and force transmitting surfaces sloping, from said root spaces to said tips, away from the other of said platens; said cooperating teeth of said tie bars having tips and root spaces, and force transmitting surfaces sloping, from such root spaces to such tips, towards said second platen; and said further cooperating teeth of said tie bars having tips and root spaces, and force transmitting surfaces sloping, from such last-mentioned root spaces to such last-mentioned tips, towards said first platen, so that during a pressing op eration with said platens locked together through said tie bars, the reaction forces produced and tending to force said platens apart will tend to pull said tie bars more firmly into engagement with said first and second platens.

15. Apparatus according to claim 13 wherein said means (h) includes means guiding said tie bars for movement towards and away from said platens in a direction having a component parallel to said path of travel and directed from said first platen toward said second platen, so that said cooperating teeth of said tie bars may engage said teeth of said first platen to pull said first platen towards said second platen along said path of travel as said tie bars are moved to their first position.

16. Apparatus according to clairn 13 wherein each tie bar includes a rear surface opposite its surface facing said platens, and said means (h) includes a pair of tie bar pulling rods, one for each tie bar, means supporting each tie bar pulling rod adjacent the rear surface of its associated tie bar for movement back and forth in a direction parallel to said path of travel and including means bracing each tie bar pulling rod against movement away from said platens in a direction at right angles to said path of travel, means guiding said tie bars for movement in a direction towards and away from said platens,

and means coupling each tie bar pulling rod with its ,i

associated tie bar for movement of a tie bar pulling rod in one direction along said path of travel to move its associated tie bar into said first position in which such tie bar engages both platens and for movement of such tie bar for pulling rod in the other direction to move its associated tie bar into said second position in which such tie bar is disengaged from said platens.

17. Apparatus according to claim 16 wherein said means (b) further includes means for moving said tie bar pulling rods, after said first platen has moved to a desired location, in said one direction thus to move said tie bars into said first position to lock said platens against movement apart relative to each other along said path of travel.

18. Apparatus according to claim 8 wherein said teeth of said first platen have tips and root spaces, and force transmitting surfaces sloping, from the said root spaces to said tips, towards said second platen; and said cooperating teeth of said tie bars have tips and root spaces and force transmitting surfaces sloping, from such root spaces 15 i to such tips, away from said second platen, so that when said first platen is positioned with the force transmitting surfaces of its teeth located partly to engage the force transmitting surfaces of said cooperating teeth of said tie bars when such teeth are moved into initial contact, then:

movement of said tie bars toward said platens, for the teeth of said tie bars fully to engage the teeth of said platens, will force said first platen `towards said second platen to exert pressure on said object.

19. Apparatus according to claim 18 'Where keach tie bar has a rear surface opposite its surface facing said platens, each said rear surface including first and second camming surfaces both inclined to said path of travel, said first camming surface meeting said second camming surface and being inclined more steeply to said path of travel than said second camming surface; and wherein said means (h) includes a pair of tie bar pulling rods, one for each tie bar, means supporting each tie bar pulling rod adjacent the rear surface of its associated tie bar for movement back and forth in a direction parallel to said path of travel and including means bracing each tie bar pulling rod against movement away from said platens in a direction at right angles to said path of travel, means guiding said tie bars for movement in a direction towards and away from said platens, each tie bar pulling rod including third and fourth camming surfaces inclined t0 said path of travel and cooperating with the first and second camming surfaces respectively of its associated tie bar, said third camming surface being inclined more steeply to said path of travel than said fourth camming surface, so that when a tie bar pulling rod is pulled for its third camming surface to move over said first camming surface of its associated tie bar, such associated tie bar is forced toward said platens at a predetermined rate, said third camming surface then moving past saidv first camming surface and said fourth camming surface commencing movement over said second camming surface, such associated tie bar then being forced toward said platens at a rate that is less than said predetermined rate.

20. A machine according to claim 1 wherein said one platen is said second platen, said cooperating locking means including hinge means connecting said tie bars to said first platen.

21. A machine according to claim 20 wherein second platen includes locking plate means, said force receiving means of said second platen being a pressure plate, said second platen furtherincluding a plurality of fixed tie rods connecting said locking plate means and said presp sure plate together with said first platen located between said locking plate` means and said pressure plate, said teeth on said side faces of said one platen being on said locking plate means.

22. A machine according toV claim 21 wherein said first platen includes apertures for said yfixed tie rods, said xed tie rods passing through such apertures to guide said rst platen during its movement along said path.

23. A machine according to claim 21 wherein said motive means comprises an actuator mounted on said,

locking plateV means, on the side thereof remote from said first platen, and a rod extending from said actuator through said locking plate means and connected with said first platen.

24. A machine according to claim 21 wherein said locking plate means includes a plate having a pair of enlarged apertures thereon, one for each tie bar, said tie bars passing through said apertures in said plate, said apertures having side surfaces opposing said teeth on said tie bars, said side surfaces constituting said side faces having said teeth thereon.

25. A machine according to claim 24 including a pair of locking pins extending through said plate in a direction transverse to said path, one said locking pin passing through each of said apertures in said plate between a vside wall of said aperture and the tie bar projecting through said aperture, each locking pin having a fiat sur- 17 face thereon and otherwise being of substantially circular cross-section, the dimensions of said teeth on said plate and tie bars and of said apertures and of said locking pins being such that when said at surfaces of said locking pins are parallel to said side walls, said tie bars can move laterally to disengage their teeth from the teeth in said plate, and when said locking pins are turned to interpose their maximum diameter between said side walls of said aperture and said tie bars, said teeth of said tie bars are held tightly in engagement with said teeth on said plate.

26. A machine according to claim 24 wherein said means (g) comprises at least one actuator extending between said tie bars in a direction perpendicular to said path, said actuator being connected to said tie bars for effecting movement thereof.

27. A machine according to claim 21 wherein said teeth and said cooperating teeth each have front and back force transmitting surfaces, and the angle between the said front force transmitting surfaces and a plane perpendicular to the axis of said tie bars is equal to the angle between said Iback force transmitting surfaces and said plane.

28. A machine according to claim 21 wherein said teeth and said cooperating teeth each have front and back force transmitting surfaces, and the angle between the said front force transmitting surfaces and a plane perpendicular to the axis of said tie bars is equal to the angle between said back force transmitting surfaces and said plane, said angle being in the range between 3 degrees and 15 degrees.

29. A machine according to claim 13 wherein said teeth and said cooperating teeth each have front and back force transmitting surfaces, and the angle between the said front force transmitting surfaces and a plane perpendicular to the axis of said tie bars is equal to the angle between said back force transmitting surfaces and said plane.

30. A machine according to claim 29 wherein said angle is in the range between 3 degrees and 15 degrees.

References Cited UNITED STATES PATENTS 1,381,854 6/1921 Wilson 18-33 1,410,291 3/1922 Gadbois 18-33 1,714,189 5/1929 Reynolds 18-33UX 1,851,138 3/1932 Smith 18--16R 2,561,021 7/1951 Groth 18-30LT 2,711,561 6/1955 Studli 18-30LV 2,865,208 12/1958 Wacht 18-16RUX 3,208,373 9/ 1965 Bachelier 18-16TX 3,23 8,576 3/ 1966 Taccone 249--183X 3,278,989 10/1966 Neubauer et al. 18-16T 3,310,842 3/1967 Fschback 18-43X 3,505,708 4/ 1970 Moslo 18-30LUX I. HOWARD FLINT, JR., Primary Examiner U.S. C1. X.R. 18-43, 30LV 

